Flocculation process and device

ABSTRACT

The present invention is in the field of laundry processes and devices. In particular the invention relates to the saving of water. It is an object of the present invention to reduce the water consumption in conventional washing methods, especially machine washing methods. It is found that the continuous pH controlled sequential dosing of an electrolyte, followed by dosing of a polymer and a solid liquid separation step during a full wash cycle of a washing machine, provides continuous clarification of the wash liquor and enables the continuous reuse of the water during said wash cycle.

FIELD OF THE INVENTION

The present invention is in the field of laundry processes and devices.In particular the invention relates to the saving of water.

BACKGROUND OF THE INVENTION

Washing processes, including laundry, mechanical dishwashing and otherhousehold cleaning processes, require large amounts of water throughoutthe world.

For example, commercially available front load washing machines useapproximately 60 litres (of water for a normal full wash cycle, top loadmachines and hand wash processes require about 180-240 litres for thesame cycle, depending on the number of rinse steps (2 or 3). Dependingon the number of rinse steps, one quarter or one third of this volume isrequired for the main wash, while three quarters or two thirds are usedfor the two or three consecutive rinse steps.

The discarded water is a burden to waste water treatment facilities, orto the surface water supply in developing countries.

JP2002119794A discloses a washing machine capable of rapidly purifyingwashing water after use by promoting flocculation of pollutantscontaining surfactant solution. It further discloses a washing machinefor the purification of washing water by utilising flocculation ofpollutants. Washing water may be pumped into a primary flocculationdevice comprising polyaluminium chloride. Additionally a control valvemay allow access of the washing water into a secondary flocculationdevice where a poly acrylamide solution may be added as a secondaryflocculant. A separation unit could remove the flocculated mass andallow the washing water to return to the washing tub.

JP2002119794A further suggests a filter for solid liquid separationselected from nonwoven fabric, a wire gauze and a filter paper. Thepresent inventors have found that the re-use of non-woven material is aproblem, while the wire gauze does not retain the flocs, and filterpaper will not sustain the pressure. It is found that flocs that areformed under the conditions of JP2002119794A cause the filter to clogafter one or a few cycles. It remains to be desired clarify water in awashing machine, without the need to replace the filter.

Similarly, JP2001054700A, JP2001300191A and JP2001286697A disclose amethod for the flocculation of dirt in laundry liquor. However, this isdone by collecting the laundry water after use and flocculating andseparating the flocs in separate holding tanks. The required time forsuch processes is considered to be too long if it needs to be done forsmall discrete parts of the wash liquor, during the process, or willrequire a second 60 L holding tank, which is also not appreciated by theconsumer.

Hence, effective separation of the flocs as obtained in the art,particularly in a continuous process remains to be desired.

Accordingly it is an object of the present invention to reduce the waterconsumption in conventional washing methods, especially machine washingmethods.

It is a further object to provide a washing process that produces wastewater which brings a lower burden on the environment, especially thesurface water.

It is yet a further object to provide a process that enables theseparate disposal of solid waste coming from the wash process.

It is yet a further object to provide a process that removes surfactantfor the wash liquor.

It is a further object of the invention to continuously clarify and/orpurify washing water, especially during the wash cycle.

Surprisingly we have found that the continuous pH controlled sequentialdosing of an electrolyte, followed by dosing of a polymer and a solidliquid separation step during a full wash cycle of a washing machine,wherein the electrolyte dose is controlled by the pH after dosing of theelectrolyte, provides continuous clarification of the wash liquor andenables the continuous reuse of the water during said wash cycle, withflocs that are easier to separate from the liquor.

SUMMARY OF THE INVENTION

Accordingly, the present invention provides a process for continuouspurification of wash water from a chamber using a sequential devicecomprising a first dosing point, in fluid communication with a firstmixing point; in fluid communication with a second dosing point, influid communication with a second mixing point; in fluid communicationwith a solid/liquid separator unit, in fluid communication with thechamber wherein the process comprises the steps of: pumping the waterfrom the chamber into the sequential device; continuous, stepped orpulsed dosing of an electrolyte composition selected from aluminium andferric salts to the wash water at the first dosing point; continuousdosing of a polymer composition comprising neutral or anionicallymodified poly acryl amide polymer (MW>100 kD) to the wash water at thesecond dosing point characterised in that the dosing of the electrolyteand the polymer is controlled by the pH of the water between the firstmixing point and the second dosing point, wherein electrolyte is doseduntil the pH drops to between 6.8 and 8.2.

In a second aspect the invention provides, a water clarification andpurification device comprising an assembly for continuous purificationof wash water from a chamber, using a sequential device comprising: afirst dosing point, in fluid communication with a first mixing point; influid communication with a second dosing point, in fluid communicationwith a second mixing point; in fluid communication with a solid/liquidseparator unit, in fluid communication with the chamber.

In a third aspect the invention provides a washing machine comprisingthe water purification and clarification device according to theinvention, wherein the chamber is the washing machine tub or a separatewash water storage tank.

These and other aspects, features and advantages will become apparent tothose of ordinary skill in the art from a reading of the followingdetailed description and the appended claims. For the avoidance ofdoubt, any feature of one aspect of the present invention may beutilised in any other aspect of the invention. The word “comprising” isintended to mean “including” but not necessarily “consisting of” or“composed of.” In other words, the listed steps or options need not beexhaustive. It is noted that the examples given in the description beloware intended to clarify the invention and are not intended to limit theinvention to those examples per se. Similarly, all percentages areweight/weight percentages unless otherwise indicated. Except in theoperating and comparative examples, or where otherwise explicitlyindicated, all numbers in this description indicating amounts ofmaterial or conditions of reaction, physical properties of materialsand/or use are to be understood as modified by the word “about”.Numerical ranges expressed in the format “from x to y” are understood toinclude x and y. When for a specific feature multiple preferred rangesare described in the format “from x to y”, it is understood that allranges combining the different endpoints are also contemplated.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to the clarification and/or purification of washwater. This enables the consumer to use less water by reusing the samewater for different steps in a wash process or even for different washprocesses. The wash process may be a laundry cleaning process, a dishwashing process or any other type of household washing process.

Accordingly, the invention provides a process for continuous wash waterpurification using a device and a process according to the invention.

The Device

Water from the chamber is transferred (e.g. pumped) into the sequentialdevice according to the invention.

The sequential device comprises a first dosing point, in fluidcommunication with a first mixing point; in fluid communication with asecond dosing point, in fluid communication with a second mixing point;in fluid communication with a solid/liquid separator unit, in fluidcommunication with the chamber comprising the remaining wash water.

In a preferred embodiment, the invention provides a washing machinecomprising an assembly for continuous purification of wash water from achamber, using a sequential device comprising a first dosing point, influid communication with a first mixing point; in fluid communicationwith a second dosing point, in fluid communication with a second mixingpoint; in fluid communication with a solid/liquid separator unit, influid communication with the chamber, wherein the chamber is the washingmachine tub, or a separate wash liquor storage tank.

Chamber Comprising the Wash Water

The chamber comprising the wash water is preferably the washing machinetub itself, but may also be an intermediate storage chamber.

For household appliances, the chamber preferably holds between 1 and 100litres of water. When the device is used in a standard top loaderwashing machine the volume is typically between 40 and 80 litres. Whenthe device is used in a standard front load washing machine or anautomatic dishwashing machine, the volume is typically between 10 and 20litres. Small scale, low-end washing machine devices for developingmarkets for washing between 1 and 5 kg of laundry, preferably between 1and 3 kg of laundry are also envisaged. For those devices the volume istypically between 10 and 20 litres of water. Industrial scale washingmachines, typically holding from 50 to 250 litres of water are alsocontemplated in the context of the present invention.

Mixing Points

The device comprises at least two mixing points, each positioned in thewater flow after the respective dosing points as discussed herein below.

First Dosing Point The first dosing point typically comprises a dosingmechanism for dosing an electrolyte composition selected from aluminiumand ferric salts to the wash water

The electrolyte composition may be a solid composition, a liquidcomposition, or anything in between, including pastes and gels.

The electrolyte may be any Al or/and Fe salt. They may be inpre-hydrolyzed form of bacisity (B=Al/OH). It is preferred that thebasicity (B) is from 10 to 90, more preferably the basicity is in therange of 40-80.

For Al-salts the minimum solubility of Al-hydroxide is typically in thepH range of 6.8-7.5 whereas minimum solubility of Fe-hydroxide typicallyranges from pH 4-8. Furthermore, the amount of solid precipitategenerated in case of the system treated with Fe-salts is high as thesolubility of Fe-hydroxide is lower than Al-hydroxide in the abovestated respective pH ranges. This may be used to tune the precipitationkinetics, for instance by means of using combinations of the Al and Feelectrolyte salts. Thus system treated with Fe-salts would also requirethe pH to be controlled less minutely and hence is more robust. Howeverthe residual dissolved Fe-salts impart colour to the water which mayhave a negative impact on laundry fabrics and hence is less preferred.Combinations of Iron and Aluminium salts are also contemplated

The dosing is done continuously, when the device is in operation, asdescribed herein below. The dosing is controlled by the pH of the waterbetween the first mixing point and the second dosing point, whereinelectrolyte is dosed to keep the pH within a range of 6.8 to 8.2, morepreferably from 7 to 7.5.

When dosing until the pH has come inside the indicated pH range, theflocs are easier to separate from the treated wash liquor than at otherpHs. Without wishing to be bound by a theory, it is thought that theflocculation kinetics that result from the process when operated untilthe pH is inside the indicated range, produce stronger and less stickyflocs that are easier to separate.

The required amount of electrolyte is dependent on the reservedalkalinity of the wash liquor and the amount of surfactant that ispresent in the wash liquor. Typically the amount of electrolyte isbetween 0.1 to 5 grams of electrolyte per litre of wash liquor,preferably more than 0.2 grams, more preferably more than 0.4 grams, oreeven more than 0.5 grams per litre of wash liquor, but typically lessthan 3 grams, more preferably less than 2 grams, or even less than 1gram of electrolyte per litre of wash liquor.

Second Dosing Point

The second dosing point typically comprises a dosing mechanism fordosing polymer composition preferably comprising a neutral oranionically modified polymer, having a high MW (>100 kD) to the washwater.

The molecular weight (MW) is typically less than 5000 kD, morepreferably less than 2000 kD, still more preferably less than 1000 kD.The polymer is preferably water soluble.

For the avoidance of doubt by D (Dalton) is meant atomic mass unit (amu,the less commonly used SI unit).

The polymer composition may be a solid composition, a liquidcomposition, or anything in between, including pastes and gels. Pastesand gels typically require more time for dissolution and are thereforeless preferred in the system according to the invention.

The polymer composition preferably comprises of neutral or anionicallymodified polyacrylamide polymer having molecular weight >100 kD.

The dosing is done continuously, when the device is in operation.

The required amount of polymer is dependent on the amount of solidsgenerated by flocculation and the amount of undissolved solids in thewash liquor. Typically the amount of polymer is between 1 to 50micrograms of polymer per litre of wash liquor, preferably between 2 and20 micrograms of polymer per litre of wash liquor.

In a preferred embodiment, the dosing is controlled by the amount ofsolids generated by flocculation and the amount of undissolved solids inthe wash liquor to further reduce the usage and minimise the depositionof the flocs in the system between the polymer dosing point and thefilter.

Mixing

After each of the dosing points the wash liquor is mixed with the dosedmaterial (electrolyte and polymer and/or pH buffer). The mixing may bedone in any conventional way. It is preferred that the mixing of washwater with the flocculants is done in a tube or Continuous Stirred TankReactor (CSTR) system. The tube is found to provide a faster process andmore efficient process. When a tube used, the length and diameter oftubes may be used to tune the residence time of mixing for a given flowrate, which will determine the efficiency of flocculation process. Thetube length and diameter are found to have an effect on the size andstrength of floc. The stronger and bigger the floc, the easier the solidliquid separation is in the continuous system. It is found that even anylon gauze filter may used, when the length of the tube is in the rangeof 5-50 meter, more preferably 5-20 meter, the flow rate is between 1-10L/min, more preferably 1-5 L/min and inner diameter of the tube isbetween 4-15 mm, more preferably 5-11 mm.

Solid/Liquid Separator Unit

After the successive dosing of the electrolyte composition and thepolymer composition to the wash liquor, flocs are formed.

The flocs are removed from the wash liquor by means of a solid/liquidseparator unit.

The solid/liquid separator unit may be a filter. The filter may be alimited use disposable filter, a long time use disposable filter or acleanable multi-use filter. A cleanable multi use filter is preferred tominimize the solid waste. The filter may be made of non-wovenpoly-propylene, acrylic, cellulose based polymers (including rayon andcotton), nylon, fluoro polymers or polyester; or a wire mesh, preferablya nylon mesh more preferably nylon mesh of 130 micrometer pore size.When in operation, the flocs are retained on the filter, while theclarified liquid is recycled back to the chamber.

Typically the filter area is related to the flow rate in such a way thatthe permeate flow rate is between 500 and 5000 LMH (litre/m2/hr),preferably at least 800 LMH, more preferably at least 1000 LMH, ore evenmore than 1200 LMH, while typically less than 4000 LMH, more preferablyless than 3000 LMH, or even less than 2200 LMH.

Typically a filter will give a back pressure of between 0.1 to 2 bar,preferably less than 1.5 bar, or even less than 1 bar; depending on theflow rate and the surface area and pore size of the filter.

Alternatively the solid/liquid separator unit may be a settler tank.However, since a settler tank inherently involved a large dead volume,this is not the most preferred option.

The solid/liquid separator unit may also be centrifugal separators likehydro cyclone, wherein the solid flocs are collected in a detachablyattachable sump, while the clarified liquid is returned to the chamber.

For the avoidance of doubt, the solid/liquid separation techniques basedon gravity (e.g. settler tanks) may yield a deposit of flocs at thebottom of the tank, when the flocs have a density that is greater thanthe density of the liquor, while the flocs may float on top when thedensity of the flocs is lower than the density of the liquor. Similarconditions apply to other gravity based separation techniques, such ascentrifugation.

The flocs that are formed typically have a diameter of between 0.5 mm-3cm. It is understood that the flocs are not perfectly spherical andgenerally have an irregular shape; for the purpose of this invention,diameter is defined as the longest distance from one side to another inthe floc, also known as the major axis of the floc.

The flocs typically have a density of between 0.5 and 2.5 g/mL, morepreferably between 0.8 and 1.5 g/mL.

The device according to the invention is characterised by a controlsystem for dosing of the electrolyte, wherein electrolyte is dosed untilthe pH of the wash water between the first mixing point and the seconddosing point drops to between 6.8 and 8.2. The control system may be anyconventional for dosing the electrolyte until the pH read-out in thewash water between the first mixing point and the second dosing point iswithin the indicated range. Preferably the dosing of the polymer at thesecond dosing point is also connected to the same control system,although it is considered in the context of the invention that thepolymer dosing is continued for at least some time after the dosing ofthe electrolyte is stopped, wherein some time is defined as any timebetween the end of the electrolyte dosing and the time that is requiredfor re-circulating the wash water through the device one time; in otherwords until the full volume of water in the system is passed by thesecond dosing point one more time.

Optionally the device comprises an additional dosing point for dosingthe detergent for washing. The dosing of detergent is preferably done inthe tub of the machine. The detergent may be a conventional liquid, orpowder. Alternatively, the detergent may be in the form of table,wherein the tablet may be a single unit dose, or where in two or moretablets may be dosed depending on the degree of soiling or on the wishof the consumer. Other formats, like detergent pellets, crystals,pearls, or other formats are also contemplated.

Process

The process for the clarification and/or purification of wash water ispreferably operated continuously in a wash process. Alternatively, theprocess may be operated by withdrawing a fraction of the wash liquor andtreating the fraction batch wise with the clarified water poured back inthe main wash tub while the washing continues. However this process mayincrease the total time required to cleanup the laundry wash liquor andan extra storage container, and is therefore less preferred.

In the process the dirty wash water is transferred into the sequentialdevice according to the invention. This is preferably done by means of apump.

Dosing of the Electrolyte Composition

The continuous dosing of an electrolyte composition selected fromaluminium and ferric salts to the wash water is done at the first dosingpoint. The first dosing point may be a liquid dosing point into thesequential device, or a solid dosing point. In case a liquid dosingpoint is used, the dosing may for example be achieved by a metering pumpor by dosing from a pressurised dosing vessel. Valves for accuratedosing are also considered. In case a solid dosing point is used, thedosing may for example be achieved by using a dosing screw or by dosingpre made tablets of the electrolyte composition, whereby the tablet sizeis such that the amount of electrolyte per tablet is between one tenthto one thousandth of the total amount of electrolyte, preferably betweenone twentieth and one five hundredth, more preferably between onefiftieth and one two hundredth, to achieve differential dosing.

Without wishing to be bound by a theory, it is found that although inregular charge based aggregation, aggregates are formed by particlessticking together, this would not work in the presence of surfactants,commonly present in cleaning/washing liquor, due to the surfaceadsorption of surfactants, causing steric stabilisation of particles. Inthe system of the present invention, flocs are formed by theprecipitation of metal hydroxides, which form a porous network andphysically sweep out the particles. This process is typically referredto in literature as “sweep flocculation”. It is found that in case ofsweep flocculation the in-situ generated Al(OH)₃ or Fe(OH)₃ may depletethe surfactant from the wash or rinse liquor. It is understood that thesurfactant gets depleted by adsorbing on the surface of positivelycharged Al(OH)₃ or Fe(OH)₃ particles. Therefore Sweep flocculation isthe preferred route for the particle aggregation, for laundry liquorcontaining both surfactants and alkalinity.

After the dosing of the material the wash water continues through thedevice and is mixed in the first mixing point, before flowing to thesecond dosing device.

The dosing of electrolyte has to follow a certain profile which isexponential in nature according to the following relation (formula 1):

C^(Electrolyte)=C₀ ^(Electrolyte) _(e) ^(−v) ₀ ^(t/V)   (formula 1)

Wherein:

C_(t) ^(Electrolyte) means the concentration of electrolyte at any timet

C₀ ^(Electrolyte) means the concentration of electrolyte at time t=0

v₀ means the volumetric flow rate at time=t at which the wash liquor isdrawn from the wash

V means is the total volume of wash liquor to be treated.

The dosing of electrolyte preferably follows the above stated profile asa continuous, step or pulsed function. C₀ depends on the concentrationof electrolyte required to flocculate the wash water in a batch process.

By applying this preferred dosing profile the pH of the water in betweenthe first mixing point and the second dosing point will remain close toconstant. To further improve the flocculation efficiency, it is alsocontemplated to co-dose a small amount of pH buffer separately ortogether with the electrolyte.

Preferred buffers may include any know buffer, having a pKa value in theindicated pH range of 6.8-8.2 as described in the electrolyte sectionabove. Preferred buffers include carbonate buffers, phosphate buffers,

Dosing of the Polymer Composition.

The continuous dosing of a polymer composition, comprising a neutral oranionically modified poly acryl amide polymer (MW>100 kD) to the washwater is done at the second dosing point.

At the second dosing point the polymer is dosed to the wash liquor.After dosing, the concentration of polymer in the line is preferably inthe range of 2-20 ppm. The actual amount dosed is depending on the totalsolid generated in the process; the more solids in solution, the morepolymer is preferred, as indicated in the polymer section above. Forexample, the polymer concentration for dirty main wash liquor istypically between 10 and 20 ppm, while the polymer dosing for the finalrinse is typically in the range of 2 and 10 ppm. It is understood thatppm means microgram per litre.

It is known that the long chain polymers can adsorb on particle surfacesand thereby bring them together to form bigger and stronger aggregates(flocs) thereby facilitates filtration, settling or separation by anyother solid liquid separation process. In other words, the polymer isthought to bridge the various precipitation nuclei to form a largeraggregate system.

After the dosing point for the polymer composition, the water flows onto the second mixing point.

The dosing of polymer is done continuously following a predetermineddosing profile.

In a preferred embodiment, the dosing is controlled by the amount ofsolids generated by flocculation and the amount of undissolved solids inthe wash liquor to further reduce the usage and minimise the depositionof the flocs in the system between the polymer dosing point and thefilter.

It is thought that the polymer's adsorption efficiency is regulated bythe surface characteristics/nature of floc in presence of surfactant. Tofavour the polymer adsorption, it is preferred that the right flocsurface characteristics in terms of surface property which can beachieved by the above indicated electrolyte dosage and therebycontrolling the pH of water.

By dosing the electrolyte until the desired pH is reached, it is foundthat this provides improved clarification of wash water, efficientadsorption of polymer onto the flocs and it maintains a minimumconcentration of dissolved metal in the treated water (wash liquor).

DRAWINGS

A schematic drawing of a system according to the invention is shown inFIG. 1.

In FIG. 1, the wash water is in the Wash tub (1). The tub is connectedto an optional valve (2) and a main pump (3), followed by the firstdosing point (6), which is further connected to a Metering pump forelectrolyte (4), which is in turn connected to an Electrolyte dosingchamber (5). The liquid then flows to the first mixing point (7),followed the second dosing point (8, which is further connected to apump for polymer (9), which is in turn connected to a polymer dosingchamber (10). The liquid then flows to the second mixing point (11), andthrough a filter (12), to be returned to the tub.

EXAMPLES

The invention will now be illustrated by means of the followingnon-limiting examples.

Example 1 pH Controlled Dosage of Electrolyte vs Constant Dosage

In this example the effect of pH controlled dosage of electrolytecompared to constant dosage is demonstrated.

In example 1 a device according to the invention is use, having a tubwith a wash liquor volume of 20 L, a first dosing point for electrolyte,a mixing coil, a second dosing point for polymer, another mixing coiland a nylon mesh (130 micrometer cut-off) filter of 0.075 m² andreturned to the main wash tub.

20 L of model wash liquor was pre made. The model wash liquor contained2 g/L of Model detergent.

Wash Liquor

Ingredient concentration Model detergent   2 g/L Kaoline 0.25 g/L

The model detergent had the following composition:

Model Detergent

Concentration Ingredients (% as is) Sodium linear alkylbenzenesulphonate (ex Reliance 16 chemicals, India) Soda (ex Tata chemicals,India) 30 Sodium Tripolyphosphate (ex Rhodia) 2 Calcite, (Forcal U, exSaurashtra Solid Industry Pvt 10 Ltd, India) Sodium carboxymethylcellulose (ex Merck) 1.5 Sodium chloride (ex Nirma chemicals limited,India) 36 Moisture 4.5

The wash liquor (20 L) was pre made and drawn from the tub at a flowrate of 2.5 L/min, the electrolyte (PAC, polyaluminium chloride (B=60))was dosed at the first dosing point at a first concentration (c₀) of 0.7g/L and then followed by the profile according to the equation offormula 1 above and put through the first mixing point (a PVC coil of 10m length, inner diameter of 8.5 mm); thereafter the polymer was dosed atthe second dosing point at a concentration of 3 microgram/L and putthrough the second mixing point (a PVC coil of 10 m length, innerdiameter of 8.5 mm); thereafter the liquid is passed through a filter(nylon gauze filter of 0.075 m² having a 130 micrometer pore size) toremove the flocs and passed back to the tub.

In comparative example A the same set up and device were used, but now,the electrolyte is dosed continuously at a constant rate to 0.2 g/L inthe wash liquor in the line after the dosing point.

The total amount of electrolyte dosed in the example and the comparativeexample is identical.

Results

The tables below show how the turbidity and the pH are changing in timefor both the filtrate and the tub.

During processing it became immediately clear in the example largeflocs, while much smaller particles were found in the comparativeexample

After 1^(st) coil Floc size After 2^(nd) coil (micrometer) Floc size(mm) Example 1  3-90 0.5-10  Comp A 0.2-1   0.0005-0.002 

It was also found that the filtrate water in the example was immediatelyclear, and also the water in the tub became clear quickly, whereas thefiltrate water in the comparative example was still turbid, consequentlyresulting in turbid wash water in the tub. Turbidity data is given inthe tables below.

Results Example 1

Tub Filtrate Time Turbidity Turbidity (minutes) (NTU) pH (NTU) pH 0 50810.88 2 4.28 7.54 5 238 10.2 1.2 7.31 10 90 9.61 1.01 7.33 15 57 7.960.75 7.24 20 34 7.46 1.2 7.2 25 16.2 7.42 0.65 7.05 30 8.02 7.16 0.816.94 35 5.11 7.03 1.04 6.8 45 2.61 6.72 4.2 6.62

Results Comparative Example A

Tub Filtrate Time Turbidity Turbidity (minutes) (NTU) pH (NTU) pH 0 51510.77 2 556 10.05 5 580 10.4 570 9.68 10 555 10.06 390 9.42 15 496 9.65262 9.19 25 174 9.11 6.93 8.05 30 103 8.81 4.02 7.48 35 51.3 8.12 1.326.94 45 32.7 7.06 58.9 6.35 47 47.2 6.91 75.3 6.27

The tables above show that the pH in the example quickly decreases tothe required value and remains constant at that value, while the pH inthe comparative example goes down following an almost linear profile.They also show that the turbidity of the filtrate in the example dropsto a very low level from the start and remains low throughout theprocess, while the turbidity in the comparative example is much higherthroughout the process, resulting in a low turbidity tub water in theexample, against a comparatively high turbidity in the tub in thecomparative example.

1. A process for continuous purification of wash water fro chamber usinga sequential device comprising: a a first dosing point, in fluidcommunication with b a first mixing point; in fluid communication with ca second dosing point, in fluid communication with d a second mixingpoint; in fluid communication with e a solid/liquid separator unit, influid communication with f the chamber (a) wherein the process comprisesthe steps of: a pumping the water from the chamber into the sequentialdevice; b continuous, stepped or pulsed dosing of an electrolytecomposition selected from aluminium and ferric salts to the wash waterat the first dosing point; c continuous dosing of a polymer compositioncomprising neutral or anionically modified poly acryl amide polymer(MW>100 kD) to the wash water at the second dosing point characterisedin that the dosing of the electrolyte and the polymer is controlled bythe pH of the water between the first mixing point and the second dosingpoint, wherein electrolyte is dosed until the pH drops to between 6.8and 8,2; and wherein the dosing of the electrolyte follows the dosingprofile according to the formula: C_(t) ^(Electrolyte)=C₀^(Electrolyte)e^(−v) ₀ ^(t/V) wherein: C_(t) ^(Electrolyte) means theconcentration of electrolyte at any time t, C₀ ^(Electrolyte) means theconcentration of electrolyte at time t=0, v₀ means the volumetric flowrate at time=t at which the wash liquor is drawn from the wash and Vmeans the total volume of wash liquor to be treated.
 2. A processaccording to claim 1, where a buffer composition is added together witheither the electrolyte or the polymer at their respective dosing points,3. A process according to claim 1, wherein the solid/liquid separatorunit comprises a: a particle filter; or b a hydro cyclone; or c asettling chamber; or combinations thereof.
 4. A water clarification andpurification device for operating the process according to claim 1,comprising an assembly for continuous purification of wash water from achamber, using a sequential device, in fluid communication with thechamber comprising: a a first dosing point, connected to an electrolytesource, in fluid communication with b a first mixing point; in fluidcommunication with c a second dosing point, connected to a source ofneutral or anionically modified poly acryl amide, in fluid communicationwith d a second mixing point; in fluid communication with e asolid/liquid separator unit, in fluid communication with f the chamber(a) characterised by a control system adapted for dosing of theelectrolyte following the dosing profile according to the formula: C_(t)^(Electrolyte)=C₀ ^(Electrolyte)e^(−v) ₀ ^(t/V) wherein: C_(t)^(Electrolyte) means the concentration of electrolyte at any time t, C₀^(Electrolyte) means the concentration of electrolyte at time t=0, v₀means the volumetric flow rate at time=t at which the wash liquor isdrawn from the wash and V means the total volume of wash liquor to betreated; and wherein electrolyte is dosed until the pH of the wash waterbetween the first mixing point and the second dosing point drops tobetween 6.8 and 8.2.
 5. A washing machine comprising the waterclarification and purification device according to claim 4, wherein thechamber is the washing machine tub or a separate wash water storagetank.